Idiopathic inflammatory myopathy (polymyositis, dermatomyositis, and related disorders) is a family of inflammatory diseases in which disease-specific autoantibodies occur and for which there is considerable indirect evidence pointing to a viral etiology. We have over the past several years, seen and studied and collected serum, blood, and muscle specimens from well over 500 patients suspected of having myositis and we have collected epidemiologic information on many patients. Our recent attention has been focussed on the mechanism of autoimmunity and on the details of tissue within the affected muscles. We have completed studies on the primary sequence of two more of the target autoantigens, isoleucyl- and (in collaboration with Paul Schimmel at MIT) alanyl-tRNA synthetase and have identified the chromosomal location of four of the target aminoacyl-tRNA synthetases. We have produced pure recombinant histidyl-tRNA synthetase (HRS) and, with Craig Hyde, made large crystals, but the x-ray diffraction studies have so far been of only low resolution. Dr. Terry O'Hanlon and Dr. Fred Miller of CBER/FDA with Dr. Raben, have identified a transcript of what appears to be the mitochondrial HRS. We have studied the cytokines and chemokines produced by circulating leukocytes (with Dr. Dennis Klinman of CBER/FDA) and by cells within affected muscle biopsies, and we have continued preparations to study the peptides found in Class I HLA antigens on the surface of myoblasts.